Seat belt retractor

ABSTRACT

The disclosed seat belt retractor can be used to suppress noise and vibration to a vehicle occupant. The seat belt retractor may comprise a spool for retracting and withdrawing a seat belt and a base frame for rotatably supporting the spool. The base frame may comprise a first supporting member, a second supporting and a spacing member for coupling the first and second supporting member at a predetermined distance. The spacing member can be a member for setting the pair of the first supporting member and the second supporting member parallel to each other

BACKGROUND

The present invention relates to the technical field of a seat beltretractor, which attaches to a motor vehicle such as an automobile orthe like, is used in a seat belt apparatus for restraining andprotecting an occupant, and retracts and withdraws the seat belt by aspool. More particularly, the present invention relates to a seat beltretractor having a base frame for rotatably supporting the spool and aseat belt apparatus having the seat belt retractor.

Up to this time, a seat belt apparatus attached to a motor vehicle, suchas an automobile or the like, restrains an occupant with a seat belt soas to prevent the occupant from moving out of the seat by inertia, thusprotecting the occupant in an emergency, such as a vehicle collisionwhere a large deceleration acts on the motor vehicle. The seat beltapparatus is provided with a seat belt retractor that performs aretracting and withdrawing operation for the seat belt and prevents theseat belt from being withdrawn in the emergency.

Conventionally, a seat belt retractor that performs the retracting andwithdrawing operations for the seat belt by a motor has been proposed,e.g., see Japanese PCT Publication No. 2003-507252 (hereinafter known asthe “'252 Publication”). In the seat belt retractor disclosed in the'252 Publication, an electric motor is disposed coaxially and in serieswith a belt reel (hereinafter, sometimes referred to as a “spool”) atone side of the belt reel in an axial direction so that a rotation ofthe electric motor is transmitted to the belt reel via a speed-reductionmechanism composed of a planetary gear speed-reduction mechanism at areduced speed. The belt reel is rotated in a belt retracting directionor a belt withdrawing direction by the rotation of the electric motor,whereby the seat belt can be retracted into or withdrawn from the beltreel.

In a seat belt retractor operated by a motor drive, such as thatdisclosed in the '252 Publication, because the motor is driven forretracting and withdrawing the seat belt and the speed-reductionmechanism is operated, which results in the rotation of the spool,vibration and noise tend to occur.

In addition, in conventional seat belt retractors, the spool forretracting or withdrawing the seat belt is rotatably supported by a baseframe, e.g., see Japanese Unexamined Patent Application Publication No.2001-347921 (hereinafter known as the “'921 Publication”). In general,the base frame is a U-shaped flat metal plate formed by a press moldingso as to be provided with left and right side walls, which directly orindirectly support the spool.

Generally, the spool, the motor, and the like in the seat belt retractorare supported at both the left and right side walls of the base framehaving a U-shape, as is generally disclosed in the '921 Publication.Further, the base frame is a flat metal plate formed by a press moldingand the left and right side walls are configured to be parallel to eachother. In order to effectively suppress the vibration and noise in theseat belt retractor, it is requested that the degree of parallelizationof the left and right side walls is obtained with high accuracy.

Accordingly, the present seat belt retractor is made in light of theabove-described problems and the object is to provide a seat beltretractor capable of effectively suppressing the occurrence of vibrationand noise.

In addition, another object of the present application is to provide aseat belt apparatus capable of effectively suppressing the transmissionof the vibration or the noise, which is caused by the seat beltretractor, to the occupant.

SUMMARY

To solve the above-mentioned problems, a seat belt apparatus accordingto one embodiment of the present invention is characterized in that itmay comprise: at least a seat belt; a spool for retracting andwithdrawing the seat belt; a base frame for rotatably supporting thespool and including a pair of a flat plate-shaped first and secondsupporting members; and a spacing member for coupling the pair of thefirst and second supporting members at a predetermined distance. Thespacing member may be a member for setting the pair of the first andsecond supporting members parallel to each other.

In another embodiment of the present invention, the seat belt retractormay be characterized in that at least one of the spacing member and thepair of the first and second supporting members includes an engagingportion. In addition, at least the other of the spacing member and thepair of the first and second supporting members includes an engagedportion to be engaged with the engaging portion.

In yet another embodiment, the seat belt retractor may be characterizedin that, the base frame can include a second frame to be attached to amotor vehicle body and the pair of the first and second supportingmembers is coupled with the second frame via a cushioning device.

Still further, another embodiment the seat belt retractor ischaracterized in that the cushioning device may be composed of acushioning member.

Moreover, the seat belt retractor may be characterized in that the seatbelt retractor can include a motor for generating a rotating drive forceto rotate the spool and a speed-reduction mechanism for transmitting therotating drive force of the motor to the spool. The motor may supportedby at least one of the first supporting member and the second supportingmember and the speed-reduction mechanism is supported by either thefirst or the second supporting member.

Furthermore, a seat belt apparatus may be characterized in that the seatbelt apparatus includes at least a seat belt for restraining anoccupant, a seat belt retractor for withdrawably retracting the seatbelt, a tongue being slidably supported by the seat belt, and a bucklefor the tongue to be detachably engaged therewith. The seat beltretractor can be the seat belt retractor according to any one ofembodiments of the present invention.

According to an embodiment of seat belt retractor, a base frame can beconfigured by coupling a pair of flat plate-shaped first and secondsupporting members by a spacing member and the first and secondsupporting members are set to be parallel by the spacing member. Thus,the degree of parallelization of the first and second supporting membersis obtained with high accuracy. As a result, the assembling accuracy canbe improved and vibration and noise caused by the rotation of the spoolcan be further suppressed.

Because the first and second supporting members can be coupled in astate that either one of an engaging portion or an engaged portionprovided in the spacing member is engaged with either one of the otherengaging portion and an engaged portion provided in the pair of thefirst and second supporting members, the first and second supportingmembers are firmly coupled with each other. Thus, the first frame can beprovided with high rigidity and firmness. As a result, the mutualdisplacement of the first and second supporting members due to a loadapplied to the spool can be securely prevented.

Furthermore, because the degree of parallelization of the first andsecond supporting members can be obtained with high accuracy asdescribed above and/or because the mutual displacement of the first andsecond supporting members can be prevented, the spool can be supportedby the first and second supporting members with high accuracy.Accordingly, the vibration and/or the noise caused by the spool can beeffectively suppressed.

Furthermore, according to another embodiment, because the base frame isdivided into the first frame for supporting the spool and a second frameto be attached to the motor vehicle body and the first frame and thesecond frame are coupled via a cushioning device, the vibration and thenoise caused by the rotation of the spool is cut off by the cushioningdevice and the transmission to the motor vehicle body is effectivelysuppressed. In this case, because the cushioning device can be formedof, for example rubber or the like, a structure of the seat beltretractor may be simplified.

In addition, according to some embodiments, transmission of thevibration and the noise caused by the rotating drive of the motor andthe operation of the speed-reduction mechanism to the motor vehicle bodycan be suppressed. In particular, when the spool is directly connectedto the motor via the speed-reduction mechanism, the frequency of thedrive of the motor and the frequency of the operation of thespeed-reduction mechanism are relatively high. However, the transmissionof the vibration and the noise to the motor vehicle body can be far moreeffectively suppressed by adopting the seat belt retractor of thepresent disclosure that is described herein.

Additionally, because the degree of parallelization of the first andsecond supporting members can be obtained with high accuracy by thespacing member, the assembling accuracy of the spool, the motor, and thespeed-reduction mechanism can be improved. As a result, the vibrationand the noise caused by the rotation of the spool, the drive of themotor, and the operation of the speed-reduction mechanism can be furthersuppressed. Also, the rotating drive force of the motor can beefficiently transmitted to the spool with little loss and thus, thetransmission efficiency can be improved, which results in theimprovement of the durability of the speed-reduction mechanism.

Because the seat belt apparatus can be provided with the seat beltretractor of the present application, the vibration and the noise causedin the seat belt retractor is cut off to the motor vehicle body.Therefore, the occupant can be prevented from the feeling of beinguncomfortable, which is caused by the vibration and/or the noise.

Still further, because the first and second frames can be coupled via acushioning device, the impact energy applied to the occupant from theseat belt by the inertia movement of the occupant can be absorbed when alarge deceleration acts on the motor vehicle in a case of a vehiclecollision or the like. Thus, an energy absorbing effect (EA effect) canbe obtained by the cushioning device.

It is to be understood that both the foregoing general description andthe following detailed descriptions are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1 shows a schematic structure of a seat belt apparatus having aseat belt retractor according to an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of the seat belt retractor used inthe seat belt apparatus according to an embodiment of the presentinvention.

FIG. 3 shows an exploded perspective view of the base frame of the seatbelt retractor according to an embodiment of the present invention.

FIG. 4 shows another exploded perspective view of the base frame of theseat belt retractor according to an embodiment of the present invention.

FIG. 5 shows an assembled perspective view illustrating the base frameaccording to an embodiment of the present invention.

FIG. 6 shows a cross-sectional view along section line VI-VI in FIG. 2.

DETAILED DESCRIPTION

Hereinbelow, various embodiments of the present invention will beexplained by referring to the accompanying drawings. FIG. 1 shows aschematic structure illustrating an example of a seat belt apparatushaving a seat belt retractor according to one embodiment of the presentinvention. In the explanation below, the directions of above, below,left and right are referred to as those in the drawings used for eachexplanation.

As illustrated in FIG. 1, the seat belt apparatus 1 of this embodimentcomprises the seat belt retractor 3, a seat belt 6, a guide anchor 7, atongue 8, a buckle 9, an electronic control unit (ECU) 10, and an inputdevice 11. The seat belt retractor 3 can be fixed to a B-pillar 2 or thelike of a motor vehicle body and driven by a motor. The seat belt 6 iswithdrawn from the seat belt retractor 3 and provided, at its end, witha belt anchor 4, which can be fixed to the floor of the motor vehiclebody or a motor vehicle seat 5. The guide anchor 7 can be attached to acenter pillar or the like of the motor vehicle body and guides the seatbelt 6 withdrawn from the seat belt retractor 3 to a shoulder of anoccupant C. The tongue 8 is slidably supported by the seat belt 6 guidedfrom the guide anchor 7. The tongue 8 is inserted and detachably engagedwith the buckle 9. In addition, the buckle is fixed to the floor of themotor vehicle body or the motor vehicle seat 5. The ECU 10 performs thecontrol operation for the motor of the seat belt retractor 3. The inputdevice transmits various input signals into the ECU 10 for the ECU 10 tocontrol the electric motor. The input device can be, for example, acollision detection device, an object detection device, or the like.

FIG. 2 shows a cross-sectional view of a seat belt retractor accordingto an embodiment of the invention.

As illustrated in FIG. 2, the seat belt retractor 3 has a base frame 12,a spool 13 for retracting the seat belt 6, an electric motor 14 forrotating the spool 13, and a speed-reduction mechanism 15 fortransmitting the rotation drive force of the electric motor 14 to thespool 13 at a reduced speed.

FIG. 3 shows an exploded perspective view of a partially exploded baseframe. FIG. 4 shows an exploded perspective view of the base frame inwhich another part of the base frame is exploded. FIG. 5 shows anassembled perspective view of the base frame.

As illustrated in FIG. 3, the base frame 12 is formed of a first frame16 for rotatably supporting the spool 13 and a second frame 17 attachedto the motor vehicle body. The first frame 16 is composed of aleft-and-right pair of rectangular flat-plate-shaped first and secondsupporting members 18 and 19 and four spacing members 20, 21, 22, and 23for coupling the first and second supporting members 18 and 19 at apredetermined distance. In the first and second supporting members 18and 19, relatively large circular openings 18 a and 19 a arerespectively formed.

As illustrated in FIG. 4, a right end face 20 a of the spacing member 20is in a proximal face-to-face contact with an inside face 19 b of thesecond supporting member 19. In addition, at a right end of the spacingmember 20, a pair of engagement projections 20 b and 20 c are formed.The one engagement projection 20 b is engaged with an engagement concaveportion 19 c of the second supporting member 19 and the other engagementprojection 20 c is engaged with an engagement step portion 19 d of thesecond supporting member 19. Furthermore, a left end face 20 d of thespacing member 20 is in a proximal face-to-face contact with an insideface 18 b of the first supporting member 18. In addition, a pair ofengagement projections 20 e and 20 f, which is identical to the pair ofthe engagement projections 20 b and 20 c, are formed at a left end ofthe spacing member 20. The one engagement projection 20 e is engagedwith an engagement concave portion 18 c of the first supporting member18 and the other engagement projection 20 f is engaged with anengagement step portion 18 d of the first supporting member 18. Inaddition, a degree of parallelization of the right and left end faces 20a and 20 d of the spacing member 20 is specified with high accuracy.

Similarly, the right end face 21 a of the spacing member 21 isconfigured to be in the proximal face-to-face contact with the insideface 19 b of the second supporting member 19. Further, at a right end ofthe spacing member 21, an engagement projection 21 b is formed. Theengagement projection 21 b is engaged with the engagement concaveportion 19 e of the second supporting portion 19. Furthermore, the leftend face 21 c of the spacing member 21 is in the proximal face-to-facecontact with the inside face 18 b of the first supporting member 18. Inaddition, an engagement projection 21 d, which is identical to theengagement projection 21 b, is formed at a left end of the spacingmember 21. The engagement projection 21 d is engaged with an engagementconcave portion of the first supporting member 18 (formed of the sameshape as that of the engagement concave portion 19 e). Further, thedegree of parallelization of the right and left end faces 21 a and 21 cof the spacing member 21 is specified with high accuracy.

In the same manner as described above, a right end face 22 a of thespacing member 22 is in a proximal face-to-face contact with the insideface 19 b of the second supporting member 19. Further, at a right end ofthe spacing member 22, an engagement projection 22 b is formed. Theengagement projection 22 b is engaged with an engagement step portion 19f (shown in FIG. 3) of the second supporting member 19, which is formedin a similar manner to the engagement step portion 19 d. Furthermore, aleft end face of the spacing member 22 is in a proximal face-to-facecontact with the inside face 18 b of the first supporting member 18. Inaddition, an engagement projection, which is formed similarly to theengagement projection 22 b, is formed at a left end of the spacingmember 22 (not shown). The engagement projection is engaged with theengagement step portion (formed in such a manner as that of theengagement step portion 18 d) of the first supporting member 18.Further, the degree of parallelization of the right end face 22 a andthe left end face of the spacing member 22 is specified with highaccuracy.

In the same manner as described above, a right end face 23 a of thespacing member 23 is in a proximal face-to-face contact with the insideface 19 b of the second supporting member 19. Further, at a right end ofthe spacing member 23, an engagement projection 23 b is formed. Theengagement projection 23 b is engaged with an engagement concave portion19 g of the second supporting member 19, which is formed in the samemanner as that of the engagement concave portion 19 e. Also, the leftend face 23 c of the spacing member 23 is in a proximal face-to-facecontact with the inside face 18 b of the first supporting member 18.Furthermore, an engagement projection formed in the same manner as thatof the engagement projection 23 b is formed at a left end of the spacingmember 23 (not shown). The engagement projection is engaged with anengagement concave portion of the first supporting member 18, which isformed in the same manner as that of the engagement concave portion withwhich the engagement projection 21 d of the spacing member 21 isengaged. In addition, the degree of parallelization of both the rightend face 23 a and the left end face 23 c of the spacing member 23 isspecified with high accuracy.

Each of the dimensions of the length between the left end face and theright end face of each of the spacing members 20, 21, 22, and 23 is alsospecified to be equal to each other with high accuracy.

The four spacing members 20, 21, 22, and 23 are connected to the firstand second supporting members 18 and 19 by penetrating fixing members,such as bolts (not shown) or the like, through attaching holes 24, 25,26, and 27 formed in the first supporting member 18 and attaching holes28, 29, 30, and 31 formed in the second supporting member 19. The firstand second supporting members 18 and 19 are screwed to the four spacingmembers 20, 21, 22, and 23, such that both the left and right end facesof each of the four spacing members 20, 21, 22, and 23 are in a proximalface-to-face contact with each of the inside faces (facing each other)18 b and 19 b of the first and second supporting members 18 and 19. Theengagement projections provided in the four spacing members 20, 21, 22,and 23 may constitute either one of “one engaging portion” or “oneengaged portion” of the present invention. The engagement concaveportions and the engagement step portions provided in the first andsecond supporting members 18 and 19 may constitute either one of “theother engaging portion” or “the other engaged portion” of the presentinvention.

Accordingly, the four spacing members 20, 21, 22, and 23 arerespectively disposed at each of the four corner portions of the firstand second supporting members 18 and 19 and they position the firstsupporting member 18 and the second supporting member 19 at apredetermined distance therebetween. Furthermore, the degree ofparallelization of both the right and left end faces of each of thespacing members 20, 21, 22, and 23 is specified with high accuracy. Inaddition, each of the dimensions of length between the left end face andthe right end face of each of the spacing members 20, 21, 22, and 23 isspecified to be equal with high accuracy. Therefore, each of the spacingmembers 20, 21, 22, and 23 specifies the degree of parallelization ofthe coupled first and second supporting members 18 and 19 with highaccuracy. Also, the engagement projections, respectively formed at boththe left and right ends of each of the spacing members 20, 21, 22, and23, are engaged with each of the engagement concave portions and theengagement step portions, respectively formed in the first and secondsupporting members 18 and 19. Therefore, each of the spacing members 20,21, 22, and 23 prevents the coupled first and second supporting members18 and 19 from being displaced from each other by a load applied to thespool 13. In such a state that the first and second supporting members18 and 19 are coupled by each of the spacing members 20, 21, 22, and 23,the openings 18 a and 19 a of the first and second supporting members 18and 19 are disposed in an axial direction keeping high concentricity.

In the upper and lower spacing members 22 and 23, coupling portions 32and 33 of the first frame 16 may be each integrally formed, as shown inFIG. 3. Both the coupling portions 32 and 33 of the first frame 16 areextended to approximately the outer faces of the first and secondsupporting members 18 and 19. The coupling portion 32 of the first frame16 located at an upper side is formed into a cylindrical shape. Innerperipheral faces of both end portions of the coupling portion 32 of thefirst frame 16 are formed into circular portions 32 a and 32 b, whichhave circular traverse cross-sections in which their lengths in theaxial direction and inner diameters are the same to each other. Inaddition, the circular portions 32 a and 32 b communicate with eachother through an inner peripheral face of a center portion of thecoupling portion 32. This inner peripheral face of the center portion isformed into a polygonal portion 32 c, whose traverse cross-section maybe polygonal, for example, regular hexagonal as shown in FIG. 3.Furthermore, though not shown in the drawings, the coupling portion 33located at a lower side of the first frame 16 is also formed into thesame shape as that of the coupling portion 32 of the first frame 16.

A pair of cylindrical cushioning members 34 and 35 can be composed ofrubber and the like. The cushioning members have penetration holes 34 aand 35 a in an axial direction whose traverse cross-section may bepolygonal, for example regular hexagonal as shown in FIG. 3. Inaddition, the cushioning members 34 and 35 are provided in such a mannerso as to be closely fitted into the end portions of the coupling portion32 of the first frame 16. The cushioning members 34 and 35 arerespectively formed of circular portions 34 b and 35 b that closely fitinto the circular portions 32 a and 32 b. Also, the polygonal portions34 c and 35 c closely fit into the polygonal portion 32 c and are formedinto the same polygon shape as that of the polygonal portion 32 c.

The pair of the cushioning members 34 and 35 may be disposed to besymmetric with each other and their respective polygonal portions 34 cand 35 c closely fit into the corresponding polygonal portion 32 c ofthe coupling portion 32. In addition, the circular portions 34 b and 35b of the respective cushioning members 34 and 35 closely fit into thecorresponding circular portions 32 a and 32 b of the coupling portion32. Furthermore, a reinforcement member 36, whose traverse cross-sectionhas the same polygonal shape as that of the penetration holes 34 a and35 a, is provided in the cushioning members 34, 35. The cushioningmembers 34 and 35 are thus attached to the coupling portion 32 of thefirst frame 16 by being inserted through the penetration holes 34 a and35 a in such a manner so as to not be able to rotate relative to thecushioning members 34 and 35. The reinforcement member 36 has apredetermined strength by integrally coupling the pair of the cushioningmembers 34 and 35 that are separately disposed to each other. Internalthreads (only one internal thread 36 a at the right end side is shown inFIG. 3) are formed at both end portions of the reinforcement member 36.Fixing members 37 and 38, such as screws, are screwed into thecorresponding internal threads.

Similarly, although not shown in the drawings, a pair of cylindricalcushioning members, a reinforcement member 40 having internal threads atboth end portions thereof (only an internal thread 40 a at the rightside is shown in FIG. 3) and the fixing members 41 and 42 (such as apair of screws) are provided in the coupling portion 33 of the firstframe 16 at the lower side in the same manner as the case of thecoupling portion 32.

In a state in which each of the cushioning members 34, 35, 39, etc. isattached to the corresponding upper and lower coupling portions 32 and33 of the first frame 16, step portions on the boundaries between thecircular portions 34 b, 35 b, etc. and the polygonal portions 34 c, 35c, etc. are in close contact with the step portions on the correspondingboundaries between the circular portions 32 a, 32 b, etc. and thepolygonal portions 32 c, etc. In addition, each of the end faces of thecircular portions 34 b, 35 b, etc. at opposite sides of the polygonalportions 34 c, 35 c, etc. shares approximately the same face with eachof the end faces of the coupling portion 32 and 33 of the first frame16. FIG. 3 only illustrates that the end face of the coupling portion 33of the first frame 16 at the lower side shares the same face with theend face of the cushioning member 39. Furthermore, in a state in whicheach of the reinforcement members 36 and 40 is attached to thecorresponding upper and lower coupling portions 32 and 33 of the firstframe 16, each of the end faces of the reinforcement members 36 and 40is configured to protrude at a predetermined amount from the end facesof the corresponding cushioning members 34, 35, 39, etc. FIG. 3 onlyillustrates that the right end face of the reinforcement member 40protrudes from the right end face of the cushioning member 39.

The second frame 17 can be formed into a flat plate shape, i.e., a flatboard is formed into a predetermined shape by a press molding process.The second frame 17 is hung across the side ends of the couplingportions 32 and 33 of the first and second supporting members 18 and 19.A pair of left and right coupling portions 43 and 44 at an upper sideand a pair of left and right coupling portions 45 and 46 (the couplingportion 45 of the second frame 17 is shown in FIG. 5) at a lower sideare provided in the second frame 17. An upper end portion of a main body17 a of the second frame 17 is bent at a right or approximately rightangle to form an upper main body 17 b. Both the left and right endportions of the upper main body 17 b are bent at a right orapproximately right angle to form an arm-like shape. Thus, the pair ofthe coupling portions 43 and 44 of the second frame 17 at the upper sideare formed. Furthermore, the pair of the coupling portions 45 and 46 ofthe second frame 17 at the lower side is formed by bending a lower partof the main body 17 a of the second frame 17 at a right or approximatelyright angle to form an arm-like shape. Circular penetration holes 47,48, and 49 are formed in the coupling portions 43, 44, and 46 of thesecond frame 17, as shown in FIG. 3. There is also a penetration hole ofthe coupling portion 45 of the second frame 17 but it is not shown inFIG. 3. In the penetration holes 47, 48, and 49, supporting portions 37a, 38 a, and 42 a of the fixing members 37, 38, and 42, whichcorresponding thereto, are supported in a fitting manner. The supportingshaft 41 a of the fixing member 41 is also supported by a penetratinghole (not shown) of the coupling portion 45 of the second frame 17 in afitting manner.

Now, an assembling process for the thus configured first and secondframes 16 and 17 will be explained. First, the coupling portions 43 and44 of the second frame 17 at the upper side are disposed in such amanner so as to sandwich both ends of the reinforcement member 36 of thefirst frame 16. The coupling portions 45 and 46 of the second frame 17at the lower side are disposed in such a manner so as to sandwich bothends of the reinforcement member 40 of the first frame 16. Then, theengaging projections 17 c and 17 d, which are formed at both the leftand right side ends of the main body 17 a of the second frame 17, arerespectively engaged with engagement concave portions 18 e and 19 hformed at the first and second supporting members 18 and 19 of the firstframe 16.

Each of the fixing members 37, 38, 41, and 42 is penetrated through eachof the penetrating holes of the reinforcement members 36 and 40 and isscrewed to each of the internal threads of the reinforcement members 36and 40. As a result, the coupling portions 43, 44, 45, and 46 of thesecond frame 17 are supported by the corresponding supporting portions37 a, 38 a, 41 a and 42 a of the fixing members 37, 38, 41, and 42,respectively. Thus, the coupling portions 43, 44, 45, and 46 of thesecond frame 17 are held between the head portions of each of the fixingmembers 37, 38, 41, and 42 and both ends of each of the reinforcementmembers 36 and 40 in a sandwiched manner.

As described above, the second frame 17 is integrally combined with thefirst frame 16 via the coupling portions 43, 44, 45, and 46 of thesecond frame 17, the reinforcement members 36 and 40, the cushioningmembers 34, 35, 39, etc., the coupling portions 32 and 33 of the firstframe 16, and the spacing members 22 and 23. Thus, the base frame 12 isbrought to completion as shown in FIG. 5.

Referring back to FIG. 2, the spool 13 is formed into a cylindricalshape, which is open at the right end and has a bottom portion 13 a atthe left end. In the bottom portion 13 a, a cylindrical rotation shaft13 b protrudes toward the left and penetrates an opening 18 a of thefirst supporting member 18.

The electric motor 14 is configured to be a known brush-less motor of aninner-rotor-type. The electric motor 14 may comprise a cylindricalstator (not shown in FIG. 2), which is fixed to a portion of a motorhousing 50 and can be composed of a coil, and a rotor that is composedof a magnet, which axially extends through and is rotated by the stator.A magnetic disc 51 is provided at a right side of the rotor and isconfigured to be integrally rotatable with the rotor. In addition, ahole sensor 52 is provided in the motor housing 50. Furthermore, arotation amount detection sensor 53 for detecting the rotation amount ofthe electric motor 14 is formed by the magnetic disc 51 and the holesensor 52. The rotation amount detection sensor 53 can be one of theinputting devices 11 and a rotation amount detection signal of theelectric motor 14 detected by the rotation amount detection sensor 53can be inputted into the ECU 10.

An attaching flange 50 a is formed at a right end of the motor housing50. The electric motor 14 is inserted into the spool 13 from the rightside in an axial direction. An annular step portion 50 b formed at theattaching flange 50 a fits into and is supported by the opening 19 a ofthe first supporting member 19. In addition, the attaching flange 50 ais fixed to the second supporting member 19 by fixing members (notshown).

As illustrated in FIGS. 2 and 6, the speed-reduction mechanism 15 isconfigured to be a planetary gear speed-reduction mechanism. Theplanetary gear speed-reduction mechanism is disposed at the left end ofthe rotor of the electric motor 14. The planetary gear speed-reductionmechanism is formed of a sun gear 54 that integrally rotates with therotor; an internal gear 55 that fits into and is fixed to the opening 18a of the first supporting member 18, a predetermined number (forexample, three are shown in FIG. 6) of planetary gears 56 that mesh withboth the sun gear 54 and the internal gear 55; and a carrier gear 57that rotatably supports the planetary gears 56. The carrier gear 57 isattached to the spool 13 and is configured to integrally rotate with thespool 13. The left end side of the spool 13 is supported by the sun gear54 via the carrier gear 57 and the planetary gears 56 in a radialdirection. The spool 13 is rotatably supported by the internal gear 55at the left end side via a thrust bearing 58 in an axial direction (thethrust direction). The right end side of the spool 13 is supported bythe motor housing 50 via a bearing 59 so as to rotate in both the radialand axial directions.

In this configuration of the speed-reduction mechanism 15, the rotationof the rotor of the electric motor 14 is transmitted to the planetarygears 56 via the sun gear 54 and the planetary gears 56 rotate. Then,the planetary gears 56 move around the sun gear 54 by its rotation.Thus, the spool 13 is rotated via the carrier gear 57 at a reducedspeed. In this case, the ECU 10 performs the control operation for theelectric motor 14 to rotate on the basis of a rotation amount detectionsignal from the rotation amount detection sensor 53.

Thus, in the seat belt retractor 3 of this embodiment, the spool 13 andthe electric motor 14 are directly connected via the speed-reductionmechanism 15 and the seat belt retractor 3 is configured such that thespool 13 is only rotated by the rotation of the electric motor 14. Inthis case, the spool 13 is rotated in either a belt retracting directionor a belt withdrawing direction depending on the rotating direction ofthe electric motor 14, i.e., a direction of a normal rotation or that ofa reversed rotation, which is controlled by the ECU 10. Furthermore, theECU 10 may perform the control operation for the rotation of theelectric motor 14 for retracting the seat belt 6 to keep the occupant Cunder restraint or to store the seat belt 6 or the ECU 10 may performthe control operation for the rotation of the electric motor 14 forwithdrawing the seat belt 6 to assist the occupant C to withdraw theseat belt 6 when wearing the seat belt 6 on the basis of a resultantinput signal from the input device 11 that performs various sensingoperations.

According to the seat belt retractor 3 of the present disclosure,because the base frame 12 is divided between the first frame 16 forsupporting the spool 13 and the second frame 17 to be attached to themotor vehicle body and because the first and second frames 16 and 17 arecoupled with each other via the cushioning members 34, 35, 40, etc.,vibration and noise caused by the rotation of the spool 13, the rotationdrive of the electric motor 14, and the operation of the speed-reductionmechanism 15 can be suppressed so as not to be transmitted to the motorvehicle body. In particular, in a case that the spool 13 and theelectric motor 14 are directly connected via the speed-reductionmechanism as in the seat belt retractor 3 of the present embodiment, thefrequency of the rotation of the spool 13, the frequency of the drive ofthe electric motor 14, and the frequency of the operation of thespeed-reduction mechanism 15 are high for retracting and withdrawing theseat belt 6. However, the vibration and the noise to be transmitted tothe motor vehicle body can be more efficiently suppressed using thedisclosed seat belt retractor. In addition, because the cushioningmember, such as rubber or the like, is used for the cushioning device,the structure of the seat belt retractor 3 can be simplified.

In the first frame 16 of the base frame 12, because the pair of theflat-plate-shaped first and second supporting members 18 and 19 arecoupled in such a manner so as to be spaced at a predetermined distanceby the spacing members 20, 21, 22, and 23 with high accuracy, the degreeof parallelization of the first and second supporting members 18 and 19can be obtained with high accuracy. As a result, the assembling accuracyof the spool 13, the electric motor 14, each of the gears 54, 55, and 56in the planetary gear speed-reduction mechanism, and the carrier 57 canbe improved. Therefore, the vibration and the noise caused by therotation of the spool 13, the drive of the electric motor 14, and theoperation of the speed-reduction mechanism 15 can be further suppressedand the rotation drive force of the electric motor 14 can be efficientlytransmitted to the spool 13 with little transmission loss, thusresulting in the improvement of transmission efficiency.

Furthermore, each of the engagement projections formed at both the leftand right ends of each of the spacing members 20, 21, 22, and 23 areengaged with the engagement concave portions and the engagement stepportions provided at the pair of the first and second supporting members18 and 19. Thus, the first and second supporting members 18 and 19 arecoupled with each other by each of the spacing members 20, 21, 22, and23. Accordingly, the first and second supporting members 18 and 19 canbe firmly coupled with each other and the first frame 16 can be providedwith high rigidity and firmness. As a result, the mutual displacementbetween the first and second supporting members 18 and 19 caused by aload applied to the spool 13 can be prevented.

Still further, as described above, because the degree of parallelizationof the first and second supporting members 18 and 19 can be obtainedwith high accuracy and/or because the mutual displacement between thefirst and second supporting members 18 and 19 can be prevented,concentricity of the openings 18 a and 19 a of the first and secondsupporting members 18 and 19 can be set with high accuracy. As a result,the concentricity of the spool 13, the electric motor 14, each of thegears 54 and 55 of the speed-reduction mechanism 15, and the carriergear 57 can be also set with high accuracy. Accordingly, the vibrationand the noise caused by the rotation of the spool 13, the rotation driveof the electric motor 14, and the operation of the speed-reductionmechanism 15 can be further efficiently suppressed. In addition, thedurability of each of the gears 54, 55, and 56 of the speed-reductionmechanism 15 can be improved.

In addition, according to the seat belt apparatus 1 of the presentapplication, because the above-described seat belt retractor 3 isprovided in the seat belt apparatus 1, the transmission of the vibrationand the noise that occurs in the seat belt retractor 3 is cut off. Thus,the occupant C can be prevented from feeling uncomfortable because ofsuch vibration and/or noise.

Furthermore, because the first and second frames 16 and 17 can becoupled via the cushioning members 34, 35, 40, etc., the impact energyapplied to the occupants C from the seat belt 6 by the inertia movementof the occupant C in an emergency, such as a vehicle collision where alarge deceleration acts on the motor vehicle, can be absorbed by thecushioning members. Thus, an EA effect can be obtained by the cushioningmembers 34, 35, 40, etc.

In addition, in the above-described embodiment, although the electricmotor 14 can be embedded in the spool 13, the electric motor 14 can alsobe provided outside the spool 13 along the axial direction of the spool13 as described in the '252 Publication or the electric motor 14 can beprovided outside the spool 13 in parallel with the spool 13.

It is natural to mention that the seat belt retractor of the presentdisclosure is applicable to a seat belt retractor without having theelectric motor 14.

The seat belt retractor and the seat belt apparatus having the seat beltretractor of the present application can be used as the seat beltapparatus for protecting the occupants by keeping them under restraintby the seat belt. It can be preferably utilized for the seat beltretractor provided with a base frame that rotatably supports the spoolfor performing the retracting or withdrawing operations of the seat beltand for a seat belt apparatus having the same.

The priority application Japanese Patent Application No. 2005-112438,filed Apr. 8, 2005, is incorporated by reference herein.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention is to be defined as set forth in the followingclaims.

1. A seat belt retractor, comprising: a spool for retracting andwithdrawing a seat belt; and a base frame for rotatably supporting thespool, wherein the base frame comprises: a pair of flat plate-shapedfirst and second supporting members for rotatably supporting the spool;and a spacing member for coupling the pair of the first and the secondsupporting members at a predetermined distance, and wherein the spacingmember is a member for setting the pair of the first and the secondsupporting member substantially parallel to each other.
 2. The seat beltretractor according to claim 1, wherein at least one of the spacingmember and the pair of the first and second supporting members comprisesan engaging portion, and wherein at least the other of the spacingmember and the pair of the first and second supporting members comprisesan engaged portion to be engaged with the engaging portion.
 3. The seatbelt retractor according to claim 1, wherein the base frame furthercomprises a second frame configured to be attached to a motor vehiclebody, and wherein the pair of the first supporting member and the secondsupporting member is coupled with the second frame via a cushioningdevice.
 4. The seat belt retractor according to claim 3, wherein thecushioning device is formed of a cushioning member.
 5. The seat beltretractor according to claim 1, further comprising: a motor forgenerating a rotating drive force to rotate the spool; and aspeed-reduction mechanism for transmitting a rotating drive force of themotor to the spool, wherein the motor is supported by at least one ofthe first supporting member and the second supporting member, andwherein the speed-reduction mechanism is supported by either the firstsupporting member or the second supporting member.
 6. The seat beltretractor according to claim 1, wherein the spacing member is aplurality of spacing members.
 7. A seat belt apparatus comprising: aseat belt for restraining an occupant; a seat belt retractor including aspool for retracting and withdrawing a seat belt; and a pair of flatplate-shaped first and second supporting members for rotatablysupporting the spool; and a spacing member for coupling the pair of thefirst and the second supporting members at a predetermined distance andfor setting the pair of the first and the second supporting memberssubstantially parallel to each other; a tongue configured to be slidablysupported by the seat belt; a buckle for detachable engagement with thetongue.
 8. The apparatus of claim 7, further comprising at least onecushioning device that couples a second frame with at least one of thefirst supporting member and the second supporting member.
 9. Theapparatus of claim 7, further comprising: a motor for generating arotating drive force to rotate the spool; and a speed-reductionmechanism for transmitting the rotating drive force of the motor to thespool, wherein the motor is supported by at least one of the firstsupporting member and the second supporting member, and wherein thespeed-reduction mechanism is supported by either the first supportingmember or the second supporting member.
 10. A seat belt retractorcomprising: a spool for retracting and withdrawing a seat belt; and abase frame for rotatably supporting the spool, wherein the base framecomprises: a pair of flat plate-shaped first and second supportingmembers for rotatably supporting the spool; a plurality of spacingmembers for coupling the pair of the first and second supporting membersat a predetermined distance, and wherein the plurality of spacingmembers are the same length.
 11. The seat belt retractor according toclaim 10, wherein at least one of the plurality of spacing memberscomprises an engaging portion, and wherein at least one of the first andsecond supporting members comprises an engaged portion to be engagedwith the engaging portion.
 12. The seat belt retractor according toclaim 10, wherein the plurality of spacing members is configured forsetting the pair of the first supporting member and the secondsupporting member parallel to each other.
 13. The seat belt retractoraccording to claim 10, wherein the base frame further comprises at leastone cushioning device that couples a second frame with at least one ofthe first supporting member and the second supporting member.
 14. Theseat belt retractor according to claim 10, further comprising: a motorfor generating a rotating drive force to rotate the spool; and aspeed-reduction mechanism for transmitting the rotating drive force ofthe motor to the spool, wherein the motor is supported by at least oneof the first supporting member and the second supporting member, andwherein the speed-reduction mechanism is supported by either the firstsupporting member or the second supporting member.